The House and Senate shouldn’t wait for President Obama to ask for formal authority for a military campaign against ISIS. Congress should reconvene immediately and get the ball rolling now.

Customarily, a president takes the first step, presenting a draft Authorization for the Use of Military Force (similar to a declaration of war), then negotiating with Congress on the campaign’s goals and scope.

But with President Obama plainly reluctant to drop his golf club and act, Congress should seize the initiative.

The world is awaiting the US response to the beheading of James Foley and ISIS’ explicit threats to attack America and raise its flag over the White House. Delay and ambivalence (the hallmarks of Obama’s foreign policy) will discourage our allies and embolden the enemy.

Congress needs to set the nation on a course to destroy ISIS, while sparing a reluctant president from having to lead and expend political capital on war.

After all, the Constitution gives Congress the responsibility for declaring war.

As Bush learned, not all authorizations are equal. In meeting the current threat, Congress will have to decide whether the goal is containment of ISIS or its destruction.

Both the enemy and foreign allies will be watching to see if Congress limits the territorial scope of battle, duration or the type of forces employed.

Joint Chiefs Chairman Martin Dempsey said last week that ISIS can be contained, but “not in perpetuity.” Noting its “apocalyptic” vision, he warned it “will eventually have to be defeated” — which will require US forces going into Syria.

On the other hand, House Democatic Whip Steny Hoyer supports the current airstrikes but says Obama must come to Congress if he wants to broaden the campaign. Several Democratic lawmakers are voicing concern about “mission creep.”

But there are likely enough Democratic votes to support authorization, and the number will grow as the atrocities continue.

And the burden of leadership has fallen on Congress, with Obama so far showing no sign of asking for authorization.

Consider his response to the beheading of a US citizen: “When people harm Americans anywhere, we do what’s necessary to see that justice is done.” What does that mean?

At the National Defense University in May 2013, he said America shouldn’t use military force “when we have the ability to capture individual terrorists; our preference is always to detain, interrogate, and prosecute.”

The Justice Department already has announced it’s pursuing a criminal investigation against Foley’s killers.

That’s ridiculous, considering the hundreds of terrorists with Western passports vowing our destruction and the training camps in Syria and Iraq spawning more. And it’s not the strategy recommended by the president’s own Joint Chiefs of Staff.

Sadly, it looks like politics could take precedence over the nation’s safety. Senate Majority Leader Harry Reid is reportedly skittish about a vote on military action before this November’s elections.

Having to take a stand on the issue could endanger Democratic incumbents, who’d have to either anger their party’s base or look weak to mainstream voters.